A simple compact wideband aperture coupled rectangular dielectric resonator antenna (RDRA) loaded with similar parasitic dielectric elements separated by low dielectric spacers as air gap layers is designed. The bandwidths of the proposed RDRAs are significantly enhanced as compared with the bandwidth of the driven DRA without an air gap. The measurement results are verified experimentally for a one parasitic element case. A bandwidth of 18% and 27% with VSWR better than 2 is achieved for double and triple gaps, respectively. It is interesting to point out that radiation patterns are stable in the entire operation band.

This paper presents a circularly polarized compact antenna based on the concept of Yagi-Uda antenna. By properly arranging three ring resonators operating at the fundamental mode, a compact Yagi-Uda like antenna is proposed to form directional pattern. This proposed antenna has comparable size with the ring resonator of quarter-wavelength, while the performances are comparable with the conventional microstrip antenna of half-wavelength. To validate the proposed design methodology, an antenna working at UHF radio-frequency identification (RFID) band is benchmarked. Both simulated and measured results are shown for comparison.

In this paper, a wide bandwidth and wide dynamic range AGC amplifier is presented. A push-pull variable gain amplifier (VGA) structure is proposed for wide dynamic rang. Moreover the bandwidth enhancement technique is used in the post amplifier design to ensure the wide bandwidth and gain of whole circuit. The experimental results demonstrate that the proposed AGC amplifier that is fabricated in 0.13 μm SiGe BiCMOS process, achieves a 23-GHz bandwidth and 36-dB dynamic rang among the recently published AGC amplifiers, whereas the power and area consumption are 57.6 mW and 1.9 mm², respectively.

A great deal of researches have so far been conducted on the analysis of eccentricity in induction machines. However, they mostly consider radial non-uniformity and neglect nonuniformity in the axial direction, but in practice, the axial non-uniformity due to rotor misalignment faults is quite common. This paper presents a modified model of a three-phase squirrel cage induction machine under different rotor misalignment conditions. For this purpose, general expressions for air gap and mean radius of induction machine, considering axial non-uniformity, have been developed. The proposed model is able to calculate the time varying inductances versus rotor angle for three-phase squirrel cage induction machines under general rotor misalignment, including static, dynamic and mixed rotor misalignment in the frame of a single program. Simulation results were verified by the experimental ones.

A compact decoupling network for enhancing the ports isolation of two coupled antennas is proposed in this letter. Parallel coupled lines (PCLs) and transmission lines (TLs) with different electrical lengths are considered to control the magnitude and phase of this decoupling network, respectively. The coupling coefficient of the PCLs is adjusted with various line widths and coupled gaps so that the magnitude of this network will be equal to that of the coupled antennas. And the electrical length of the series TLs can be controlled to make the signals of coupled antennas and decoupling network out of phase. Thus, the mutual coupling between the coupled antennas can be canceled. A prototype is fabricated on a RO4003 print circuit board (PCB) for demonstration. The measured results agree quiet well with the simulation ones. High antenna isolation and good matching are simultaneously achieved at the center frequency, i.e., 925 MHz for global system mobile communications (GSM) which shows the compact decoupling network is suitable for reducing the isolation of size limited multi-antenna systems.

Based on technical analysis and budget link experimentation, the main purpose here is to show improvement of HF half loop antennas in terms of signal-to-noise ratio (SNR) and stealthy for a combat ship. A special designed HF antenna brings a high quality communication over 1000 NM. A suitable integration of a HF half loop antenna at ship corners contributes to the ship stealthy. This paper shows the antenna performance and the benefit of the completely body integrated HF half loop antenna regarding whip antennas. The corresponding SNR is 15 to 20 dB better than for a conventional antenna.

A highly sensitive, passive relative humidity (RH) sensor using polyvinyl-alcohol (PVA) dielectric film is presented. For the first time, PVA is investigated in microwave RF sensing devices for low cost, high resolution and accurate chipless RH sensor realization. Comparative study with traditional humidity sensing Kapton polymer is presented to validate superior performance of PVA film. Results are presented for two different passive high Q resonators to validate sensing performance in wide applications. Moreover, a new sensing parameter is described to investigate sensitivity measurement through resonance frequency and Q factor variation. The RH sensor has the potential to be integrated with mm and μm-wave high frequency passive RFID for ubiquitous sensing.

Constrained Least Mean Square (CLMS) algorithm is used to adapt the antenna array weights. CLMS in its simple form fails to capture the Signal of Interest (SOI) if there is an error in the Direction of Arrival (DOA) estimation. Moreover, it will consider the SOI as an interferer and create null in the desired DOA. The large gain will be towards the detected wrong direction. Derivative constraints and Bayesian beamformer are two techniques used to overcome such a problem. Derivative constraints destroy a lot of Degrees of Freedom (DOF). Bayesian beamformer destroys only one DOF but vulnerable to binning error. The proposed algorithm overcomes the problem of binning error in the Bayesian beamformer with only one extra DOF.

The near-field surrounding devices can be arbitrarily sculpted if they are placed inside a spatially variant anisotropic metamaterial (SVAM). Our SVAMs are low loss because they do not contain metals and are extraordinarily broadband, working from DC up to a cutoff. In the present work, a microstrip transmission line was isolated from a metal object placed in close proximity by embedding it in an SVAM so that the field avoided the object. Our paper begins by outlining a simple finite-difference modeling approach for studying transmission lines embedded in SVAMs. We then present our design and experimental results to confirm the concept.

The study of this paper focuses on the power angle spectrum (PAS) of the satellite communication downlink in rain environment at millimeter-wave bands. The two-dimension angle distribution expression of the incoherent intensity of the ground receiving antenna in rain is deduced in detail. The coherent intensity is discussed according to the first-order multiple scattering approximation theory. The calculation model of PAS is given based on the coherent intensity and the incoherent intensity angle distribution. Based on the Marshall-Palmer raindrop size distribution, the rain-induced attenuation coefficient γ = ρ<σ_t>, as well as the average scattering amplitude function of rain area, is calculated and discussed by Mie method; the two-dimension and the one-dimension PASs are simulated and analyzed at different incident angles for different rain rates, frequencies and polarizations. The PAS model and the simulation results given in this paper are important for the quantitative evaluation of the impacts of rain environment on MMW MIMO channel characteristics.

A new planar inverted-F antenna with a very large bandwidth starting from 817 MHz to 11.5 GHz (VSWR < 3) is proposed as an alternative for high performance mobile phones intended to cover the major part of the mobile phone frequencies worldwide as well as the ultra-wideband (UWB) frequency range. A prototype of the antenna was constructed and the reflection coefficient and radiation patterns were measured to demonstrate an adequate radiation performance. The antenna dimensions of 4 x 2.5 x 0.5 cm³ are compatible with the requirements imposed by the most recent commercially available smartphones. Besides, the easy construction without a matching network or a complicated geometry is an additional feature that can be reflected in low fabrication cost.

A type of closed exterior algebra in R³ under the cross product is revealed to hold between differential forms from the three Whittaker scalar potentials, associated with the fields of a moving electron. A special algebraic structure is revealed in the context of Clebsch reparametrization of these scalars, and a special prescription for the construction of permutation invariant electromagnetic fields is given as well as a superposition with parallel electric and magnetic components.

A compact shorted annular patch antenna for global positioning system is presented in this paper. Multipath-rejection capability is realized with two stacked shorted annular patches (SAP). The broadband characteristic of the (-10 dB return loss) input impedance bandwidth and the 3 dB bandwidth of axial ratio is achieved by employing capacitively coupled feed structure while the shorted pins located between the upper and the lower patches will realize the impendence matching of the high frequency, which can cover L5/L2/L1 bands for GPS and the relative input impedance bandwidth can achieve 50.6%. The size is 0.3λ×0.3λ for 1.1 GHz.

An analytical formulation is developed for an axial slot on an infinitely long conducting circular cylinder eccentrically coated with dielectric and partially embedded in a ground plane. A computer program has been developed based on the resulting formulation. The problem is highly significant since the ground plane could be the body of an aircraft, a ship, or any other mobile system. The effect of the ground plane can be used to enhance the radiation characteristics in some cases. It is also a support for the antenna instead of using other mechanical mounting supporting system. Numerical results for different antenna configurations are illustrated. The results show that how one may shape the pattern by offsetting the slotted cylinder from the center of the dielectric coating.

This paper introduces a modified enhanced transmission-line theory to account for higher-order modes while using a standard transmission line equation solver or equivalently a Baum, Liu and Tesche (BLT) equation solver. The complex per-unit-length parameters as defined by Nitsch et al. are first cast into an appropriate per-unit-length resistance, inductance, capacitance and conductance (RLCG) form. Besides, these per-unit-length parameters are modified to account for radiation losses with reasonable approximations. This modification is introduced by an additional per-unit-length resistance. The reason and explanations for this parameter are provided. Results obtained with this new formalism are comparable to those obtained using an electromagnetic full-wave solver, thus extending the capability of conventional transmission line solvers.

This article describes a method of guiding a moving ferromagnetic sphere. By using a magnetic field, it is possible to confine a moving object such as a steel sphere to motion along a curve. We have designed and built a device that uses the magnetic field in the gap of a steel tube to trap and guide a steel sphere along a circular path solely by a magnetic restoring force. A simple relationship between tangential velocity and magnetic field strength in the gap is developed. Excellent correlation between analytic, simulated, and measured results are shown.

When performing electromagnetic material characterization, an error analysis should be performed to determine the sensitivity of the extracted permittivity and permeability. Traditional error analysis methods such as the error propagation method and Monte Carlo simulations can pose difficulties when analyzing free space material characterization methods. This paper thus shows how interval analysis can be implemented to perform error analysis on free space material characterization methods and provide an alternate means to perform error analysis. Background is presented on interval representations and interval functions, and a procedure for performing error analysis with interval analysis is presented. An error analysis is performed on the free space implementation of the layer-shift method with interval analysis and the subsequent standard deviations computed with interval analysis are compared to standard deviations computed through Monte Carlo simulation.

In this paper, a four-band metamaterial absorber (MA) based on flower-shaped structure is proposed. The design, simulation, fabrication, and measurement of the absorbers working in four bands are presented. Simulation results show that the MA has four distinctive absorption peaks at frequencies 6.69 GHz, 7.48 GHz, 8.67 GHz, and 9.91 GHz with the absorptivity of 0.96, 0.99, 0.99 and 0.98, respectively. Experiment results matches well with the simulation. Both experiment and simulation results exhibit that the MA are polarization-insensitive for TE wave and TM wave. The flower-shaped structure is also suitable for designing of a four-band THz and even higher frequency MM absorber, which would be a promising candidate as absorbing elements in scientific and technical applications.

A new SAR radiometric terrain correction method was proposed to reduce the terrain effects in sloped regions. Based on this method, a procedure for polarimetric SAR terrain effect reduction was proposed, including geometric correction, shadow detection, radiometric terrain correction, and polarization orientation angle shift compensation. Experiments using RADARSAT-2 polarimetric SAR data of the Three Gorges Area, China demonstrated the effectiveness of the proposed radiometric terrain correction method. Both visual and quantitative analyses showed that after the proposed radiometric terrain correction method was applied, the contrast between different slopes that caused by local incidence angle differences, foreshortening, and layover was significantly reduced. The difference of backscattering intensity on slopes facing the radar sensor and facing away from the sensor was reduced from 12.5 dB before radiometric correction to 1.3 dB. The overall accuracy of land use / land cover classification was improved by 11.2 percent using the terrain corrected polarimetric SAR data.

In this paper, a nontrivial local oscillator uncorrelated phase noise analysis is proposed for frequency synthesizer of a passive millimeter-wave Synthetic Aperture Interferometric Radiometer (SAIR) imager BHU-2D designed for concealed weapon detections on human bodies with high imaging rates. The frequency synthesizer provides local oscillator signals for both millimeter-wave front-ends and intermediate frequency I/Q demodulators for the receivers. The influence of local oscillator uncorrelated phase noise in different offset frequency ranges on the visibility phase errors have been systematically investigated, and the corresponding system level visibility specifications are drawn. The integrated RMS phase error has been applied to set uncorrelated phase noise requirements in the most critical offset frequency range for visibility error control. The synthesizer design is given, and measurement results have proved that the visibility phase error requirement is achieved by the PN analysis method proposed with system-level visibility error tests performed. To conclude, the phase noise effects on SAIR visibility phase errors are investigated by theory, and are properly limited by the PN requirement analysis method to ensure that the system-level visibility phase error specification is satisfied.